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    <script>
        const arr = [1,2,3,4,5];
        arr[Symbol.iterator] = function* () {
            yield 3;
            yield 4;
            yield 5;
            yield 6;
        }
        console.log(Object.getOwnPropertySymbols(arr.__proto__));
        for (const iterator of arr) {
            console.log(iterator);// 3 4 5 6
        }
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